Acrylonitrile-vinyl lactam polymer blend textiles light stabilized by treatment withhydroxyl ammonium sulfate and sulfuric acid and products produced thereby



Jan. 26, 1960 A. s. MESSER 2,922,693

ACRYLONITRILE-VINYL LACTAM POLYMER BLEND TEXTILES LIGHT STABILIZED BY TREATMENT wITE HYDROXYL AMMONIUM SULFATE AND SULFURIC ACID AND PRODUCTS PRODUCED THEREBY Filed Dec. 28, 1956 INVENTOR.

fl/ber/S. Measer BY Albert S. Messer, Concord, Califi, assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Application December 28, 1956, Serial No. 631,257 5 Claims. c1. 8-1155) This invention relates to the provision of vinyl lactain v United States Patent 0 l polymer-containing acrylonitrile polymer synthetic textile fibers and the like that have been rendered stable to the deleterious effects of light.

Certain vinyl lactam polymers, particularly polyvinylpyrrolidone, are exceptionally well adapted for employpolymer articles, particularly polyacrylonitrile fibers and the like, including filaments, yarns, films and related structures. For convenience, the various shaped articles that may be fabricated from synthetic, linear, fiberlactam polymers are incorporated in acrylonitrile polymer synthetic textile fibers, certain difficulties may also attend such practice.

By way of illustration, when vinyl lactam polymer-containing acrylonitrile polymer fibers areintended for employment in their manufactured 1 White and undyed condition, objectionable discoloration (as evidenced by assumption of a definite and visually noticeable yellowishness) may occur upon exposure to light. The natural instability of the vinyl lactam polyrnerecontaining acrylonitrile polymer fibers to ultra violet "lightengenders such result. This phenomenon, as is apparent, tends, as a practical matter, to limit the otherwise generally utile character- 'istics of vinyl lactam polymer-containing acrylonitrile "polymer fibers to employment in colored textile materials to avoid the obviously undesirable consequences that 1 might accrue in their utilization for the fabrication of uncolored, naturally white yarns and fabrics. be advantageous to overcome this deficiency in the indigated type of synthetic textile fibers.

It would Therefore, it is principally the objective of the present invention to provide light stabilized vinyl lactam polymer-containing acrylonitrile polymer synthetic textile fibers and the like that could be satisfactorily employed as a naturally white and undyed textile material which would be substantially-free from tendencies to discolor upon exposure to light, including ultra violet light, in

the course of its useful life. Other objectives and advantages ancillary. to the principal objective that may be real ized by practice of the invention are manifest in the ensuing description and specification.

In accordance with the present invention, vinyl lactam polymer-containing acrylonitrile polymer fibers may advantageously be rendered stable to light by a-treatment which comprises subjecting them to an aqueous solution of hydroxyl ammonium sulfate containing a very small proportion of sulfuric acid. Beneficially, the treatment is conducted upon the fibers in a clean and uncontaminated condition, as by treating them subsequently to a scouring operation. Preferably, the aqueous treating solution of hydroxyl ammonium'sulfate that is employed contains at least about 8 percent by weight of the ment as dye-assisting adjuvants in shaped acrylonitrile peratures.

2,922,693 Patented Jan. 26,- 1950 reagent and from about 0.5 to 5 percent by weight of solution that is employed contains about 10 percent by 2 weight of hydroxyl ammonium sulfate and from about 1'to 2 percent by weight of sulfuric acid, both based on fiber weight. g

The treatment may be conducted at any desired temperature although temperatures in the 60 C. range are frequently quite suitable for its accomplishment. Usually the treatment may be terminated with satisfactory results after periods of about A; hour, especially at temperatures of about 60 C. Sometimes, however, longer treatments may be required at lower temperatures while shorter periods may sufiice at more elevated tem- Naturally white and undyed vinyl lactam polymer-containing acrylonitrile polymer synthetic textile fibers that have been treated in accordance with the present invention have their stability to light greatly enhanced, frequently six or more times (when expressed as a function of the time period under a given light exposure that is required to produce a visually discernible discoloration) in comparison with untreated fibers of the same type. Not only does the treatment of the present invention account for the indicated benefits, it provides further amelioration of a positive nature in actually whitening the appearance of a treated fiber of the indicated variety to a measure that is definitely observ- ,able over its untreated, naturally occurring apparent whiteness. A specimen of an hydroxyl ammonium sulfate stabilized vinyl lactam polymer-containing acrylonitrile polymer fiber is schematically represented, in an exaggerated perspective, in the accompanying drawing. Advantageously, the vinyl lactam polymer-containing acrylonitrile polymer fiber that may be treated in the practice of the invention is derived from a fiber-forming acrylonitrile polymer that contains at least about 85 percent by weight of acrylonitrile polymerized in the polymet molecule and in which 'there is intimately incorporated a minor proportion of the vinyl lactam polymer as a dye-assisting adjuvant. More advantageously, the

,vinyl lactam polymer-containing fiber is derived from polyacrylonitrile. While polyvinylpyrrolidone may be incorporated with particular benefit as a dye-assisting adjuvant in such synthetic textile fibers, other vinyl lactam polymers may also be satisfactorily utilized for an equivalent purpose. These include various dye-receptive copolymers of vinyl pyrrolidone and polymers and copolymers of other vinyl lactam monomers such as vinyl caprolactam. When vinyl lactam copolymers are utilized, it is frequently desirable to employ those that contain at least about 60 or even 80 percent by weight of thevinyl lactam monomer polymerized in the copolymer -molecule.

lonitrile polymer.

Generally, it is beneficial for a vinyl lactam polymercontaining acrylonitrile polymer fiber to contain up to 20 percent by weight of a dye-receptive vinyl lactam polymer in initimate physical incorporation in the acry- It may frequently be of greatest advantage when between about 6 and 12 percent by weight of the vinyl lactam polymer, particularly polyvinylis in a swollen or gel condition.

tion, rinsed with water and dried. under exposure to ultra violet light in a standard Atlas Various techniques and procedures may be invoked for providing a vinyl lactam polymer containing acrylomtrrle polymer fiber of the indicated variety. For ex- 7 ample, the vinyl lactam polymer may be uniformly in- 'corporated in the desired quantity in a fiber-forming --acrylonitrile polymer composition prior to spinning it into fibers in order to prepare the desired dye-receptive synthetic textile fiber product. Advantageously, however, the acrylonitrile polymer fiber may be a wet spun product in which the vinyl'lactam polymer is intimately incorporated by impregnation of the dye-assisting adjuvant from an aqueous solution thereof while the fiber Thus a fiber-forming polymer of acrylonitrile (such as polyacrylonitrile) may be prepared as a spinning solution by dissolving it ina suitable solvent, such as an aqueous 6O percentby weight zinc chloride solution, and extruded in solution into a coagulating bath therefor to initially form an aquagel filamentarystructure in which the vinyl lactam polymer may conveniently be incorporated by subjecting the'aquato enhance their dye-receptivity, the known procedures are not of particular benefit for improving the light stability of vinyl lactam polymer-containing acrylonitrile polymer fibers of the nitrile alloy variety that is comprehended by the present invention. Neither dothey espe- Fadeometer." Noticeable discoloration of the fiber did not occur until lapse of a '120 hour period. To "the contrary, until the break point, the whiteness of the fiber became visibly more intense during the exposure, despite the fact that the initial whiteness of the treated fiber was discernibly greater than thatofthe same synthetic nitrile alloy fiber in a naurally white, untreated condition. In comparison, an untreated sample of the fiberbroke to an objectionable yellowish shade of discoloration after only 20 hours of exposure in the Fadeometer.

Similar results were obtained when the same hydroxyl ammonium sulfate treatment of the vinyl lactam polymercontaining acrylic fiber was conducted at a temperature of 80 C. and when a similar treatment was conducted with 10 percent on the weight of the ,fiber of hydroxyl ammonium sulfate in water containing 1 percent on the weight of the fiber of sulfuric acid. "Similar results were also obtained with a like hydroxyl ammonium sulfate treatment that was conducted at a temperature'ofrabout 95 C.

What is claimed is:

1. The improvement in the textile art .for treating a synthetic textile fiber of a polymer blend composition of (1) at least about 80 weight percent, based on the weight of the dry fiber, of (A) a fiber-forming acrylonitrile polymer that contains in the polymer molecule at least about 85 weight percent of polymcrizedacrylonitrile in an intimate'blended mixture with (2) a minor proportion of up to about 20 weight, percent, based on the weight of the dry fiber; of (B) a dye assisting vinyl lactam polymer that contains in the polymer at least about 60 weight percent of polymerized vinyl ,lactam cially serve to better the natural whiteness of such nitrile alloy fibers, 'or even of the conventional varieties 'of prototype acrylic fibers that are comprised essentially completely of acrylonitrile polymers. Thus, such known treatments of the prior art in which hydroxyl amine,

sulfate solutions that contain sodium carbonate are applied to conventional acrylic fibers do not produce results equivalent or even commensurate with those that may be attained by practice of the present invention. Acrylonitrile polymer fibers that contain vinyl'lactam' polymers as dye-assisting adjuvants are not rendered markedly stable to light or whitened when they are subjected, under any conditions of treatment, to soda ash, including solutions of hydroxyl ammonium sulfate.

By way of further illustration, about 5 grams of a 5-" 'milliliters of water and subsequently rinsed clean in distilled water.

The fiber was then immersed in'another 150 milliliters of water that contained 10 percent by weight, based on the weight of the fiber, of hydroxyl ammonium sulfate and about 2 percent on the'weight of the fiber of sulfuric acid. The treating solution was maintained at a temperatureof about 60 C. After 30 minutes, the fiber was removed from the treating solu- It wasthen tested monomer, which improvement comprises immersing said fiber in an aqueous solution that contains at lcastIabout '8 percent by weight of hydroxyl ammonium sulfateand between about 0.5 and 5 percent by weight of sulfuric acid, both based on the weight of the .fiber,,until said'fiber is rendered more stable to light.

.2. The process of claim 1, wherein said fiber .isim- .mersed in said acidified solution while it is warmand wherein said solution contains about 10 percent. by weight of the hydroxyl ammonium sulfate, based on the weight of the fiber.

3. 'The process of claim 1, wherein said synthetic-textile fiber is comprised of polyacrylonitrile in which there is intimately incorporated an amount between about 6 and 12 percent by weight, based on the weight of-dry fiber, of polyvinylpyrrolidone as a dye-assisting adjuvant.

4. The process of claim 1, wherein said fiber is immersed in said acidified solution at a temperature of about C. for a periodof time not in excess of about /2 hour.

5. As an improved article ofmanufacture, a treated synthetic textile ,fiber obtained as the productof the ,process of claim 1.

References'Cited in the fileof this patent UNITED .STATES PATENTS 2,146,735 Hale .Feb. 14, 1939 2,514,363 :Banes July 11, 1950 2,792,276 Kaupin May 14,

OTHER REFERENCES Ham: Textile ReS.JOl11,., July 1954,; pp. 597,-6fl4rand 607. 

1. THE IMPROVEMENT IN THE TEXTILE ART FOR TREATING A SYNTHETIC TEXTILE FIBER OF A POLYMER BLEND COMPOSITION OF (1) AT LEAST ABOUT 80 NWEIGHT PERCENT, BASED ON THE WEIGHT OF THE DRY FIBER, OF (A) A FIBER-FORMING ACRYLONITRILE POLYMER THAT CONTAINS IN THE POLYMER MOLECULE AT LEAST ABOUT 85 WEIGHT PERCENT OF POLYMERIZED ACRYLONITRILE IN AN INTIMATE BLENDED MIXTURE WITH (2) A MINOR PROPORTION OF UP TO ABOUT 20 WEIGHT PERCENT, BASED ON THE WEIGHT OF THE DRY FIBER, OF (B) A DYE ASSISTING VINYL LACTAM POLYMER THAT CONTAINS IN THE POLYMER AT LEAST ABOUT 60 WEIGHT PERCENT OF POLYMERIZED VINYL LACTAM 